Friday, March 18, 2011

Nuclear Meltdowns 101

[Update: The longer this disaster goes on, the more news articles appear confirming my suspicions from the very beginning. As they do, I add links to them below. So far, cooling has failed, and containment has failed. Next, radioactive lava will leak out of what were once the Fukushima nuclear reactors. The new feel-good mantra is "It's not as bad as Chernobyl." But it is already safe to conclude that the world is no longer safe enough (that is, economically, socially or politically stable enough) for nuclear power to exist. So please do the following exercise: take a map, mark every nuclear installation around where you are, draw a 50km radius circle around each, and then start seeing to it that you, your family and your friends are not in any of these circles. Pay attention to prevailing winds and coastal and ocean currents, which should extend your personal nuclear exclusion zone. Take a look around: there is no longer the money or the political power or even the technical expertise to immediately shut down and properly dismantle all of these installations and to store the nuclear waste in a way that will require zero maintenance for the thousands of years it will stay lethal. The best we can do now is evacuate ourselves ahead of time, and hope for the best.]

I am no nuclear expert, and that is probably a good thing. I did do a lot of reading about Chernobyl back when it happened. And now I am, as I was then, and as I am sure many of you are, getting really fed up with incomplete, inaccurate, misleading and generally unsatisfactory explanations that are being offered for what is going on at Fukushima. Either information is not available, or it is a flood of largely irrelevant technical minutia designed to thrill nuclear nerds but bound to bamboozle rather than inform the general reader. And so, for the sake of all the other people who aren't nuclear experts and have no ambition of ever becoming one, here's what I have been able to piece together.

Just hydrogen? Or a chain reaction?

What do they mean when they say “hydrogen explosions”? The hydrogen gas is being vented from inside the reactors and from spent fuel pools that are directly above them. Since it is very hot, it explodes as soon as it mixes with the outside air. It is formed from the rapid oxidation of the zirconium pipes that hold in the pellets of nuclear fuel. At Fukushima, some of the fuel pellets are made with uranium, while others are made with plutonium from reprocessed nuclear weapons. Zirconium is a metal which, like aluminum, instantly forms a thin, protective layer of oxide on contact with air, but doesn't oxidize further—unless it is heated up, that is. The zirconium-clad fuel rods must be kept submerged in water at all times, ocr they do heat up, and then the zirconium cladding oxidizes (burns) very rapidly and disintegrates into a powder. This is already enough information to tell us that a lot of the “fuel rods” at Fukushima are no longer rod-shaped, because the zirconium cladding has disintegrated, and that the fuel pellets must have fallen out and accumulated at the bottoms of the reactor vessels, where they are packed close together and heating up further. How much further they heat up will determine whether they will melt through the bottoms of the reactors. If they do, they would probably melt into the ground below and form a large pancake of hot, molten slag, which will slowly crumble into radioactive dust over many years, as has happened at Chernobyl. There is also a small chance that the fuel pellets will “go critical,” if the mass of them becomes sufficiently compact to restart the nuclear chain reaction; if that happens, the telltale tall brown cloud should be easy to spot from as away as Tokyo. This seems unlikely, but then nobody seems to be able to definitively rule it out either.

What do they mean when they say that they are cooling the reactor with seawater? Seawater is corrosive, and is probably the worst coolant imaginable. Normally, nuclear reactors are cooled with fresh, filtered, deionized water. The crew at Fukushima used seawater because they had no other choice. When the cooling pumps failed because the tsunami caused a blackout, they called in the fire brigade, and the fire engines there apparently use seawater. The reactor cooling systems are plumbed with stainless steel pipes, which degrade rather rapidly on contact with sea water because of the chlorine in it, especially if they are hot (which they are). At Fukushima, “containment” has already become a relative term, since the reactors are vented to the outside air in any case to keep them from bursting, but once these pipes disintegrate (a process that might take a few days to a few weeks) the containment vessels will become riddled with holes, letting in outside air and, if by then there is any zirconium left to burn, possibly causing hydrogen explosions inside the reactors, compromising them further. Their radioactive contents will then be carried to the atmosphere in aerosol form. We will probably know when that happens because the Geiger counters in the area will peg out. Nothing has been said about the destination of the copious amounts of now contaminated seawater that is being pumped through the damaged reactors and spent fuel pools. At Chernobyl, the water that that was used to "cool" the by then nonexistent reactor formed a large radioactive lake which threatened to poison Pripyat river. At Fukushima, we must suspect, all of that contaminated seawater is draining straight back into the Pacific, where tidal currents will carry it up and down the coast, contaminating the entire coastline with long-lived radioactive elements. Which brings us to a very general question:

What is the difference between radiation and radioactivity? This is a basic enough distinction, but, listening to the news coverage, I have observed a great deal of confusion. (Some of it seems intentional, if not malicious: I heard some nuclear expert/twit (a retired Oxford don, I think) on NPR explain how "wadiation" can be "thewapeutic" and never once did he mention "wadioactivity," and it made me quite mad.) Do not use the two terms interchangeably unless you want to sound like you don't know what you are talking about. Radiation, of a non-lethal kind, is what you get from a light bulb, an X-ray machine, at the beach or in a tanning booth. Radioactivity, or radioactive contamination, is what you get when a nuclear bomb or a nuclear power plant explodes, and it stays around and produces radiation for years. Both radiation and radioactivity are invisible and hard to measure, but that's where the similarity ends. Radiation consists of subatomic particles that generally go in straight lines at close to the speed of light. Given enough radiation, initially non-radioactive materials can in turn become radioactive. Radioactivity, on the other hand, is caused by radioactive materials, which decay into other materials, some also radioactive, some stable, plus some radiation, at some rate, either quickly or not so quickly. Uranium and plutonium hang around for many thousands of years. Radioactive substances can be pulverized and carried up into the atmosphere by explosions (not necessarily nuclear ones) in which case they drift with the wind for thousands of kilometers and pollute huge stretches of land and ocean. Exposure to excessive levels of radiation causes radiation poisoning, from which people can fully recover, while the various radioactive elements pollute the environment and are taken up by living organisms in a wide variety of ways, many of them not yet understood by science, poisoning them and causing a wide assortment of cancers and genetic defects. Some may be flushed out, while others become lodged in the lungs or in the bones for the life of the individual, where they remain radioactive, weakening immune systems, causing cancers and birth defects and shortening lifespans. I once spent a few hours at the airport in Minsk, waiting for a flight to Frankfurt with a group of “Chernobyl children” being flown out for treatment. They were quite a sight!

What about these “spent fuel pools” that keep catching on fire? Well that's probably the most insane thing about the nuclear power industry. They haven't figured out what to do with the spent fuel rods, so they store them tightly packed in pools of water directly at the site, or, in the case of Fukushima, since land in Japan is at such a premium, stacked directly on top of the reactor itself. The reactors at Fukushima are quite old, and so their spent fuel pools are packed full. The spent fuel rods, which accumulate over the entire lifetime of the power plant, have to be kept submerged to keep them cool, or the zirconium cladding burns away (causing hydrogen explosions) and the fuel pellets accumulate at the bottom of the pool, burning through it if the fuel is fresh enough (which, in some cases, it might be). The result is the same as with the fuel rods disintegrating inside the reactor itself, except that here there is no containment vessel to keep (at least some of) the radioactive material out of the environment.

Why do we have nuclear energy in the first place? This all sounds completely insane, doesn't it? Well, if it weren't for the nuclear bomb, anyone who proposed building a commercial fission reactor would have been laughed out of the room. But having nuclear bombs (which are by far the scariest things on the planet) makes nuclear fission reactors that much less scary, relatively speaking. And the reason we have nuclear bombs is because the only thing scarier than a nuclear bomb is not having one, since that opens you up the possibility of having one dropped on you by someone who does, such as the USSR (in theory) or the USA (as an historical fact). Compared to nuclear bombs, nuclear reactors seem "peaceful," although this is clearly not the case. Compared to nuclear reactors, nuclear bombs are as safe as houses, because they don't start a chain reaction until somebody pulls the trigger, whereas nuclear reactors maintain a controlled chain reaction during most of their existences. It's like comparing having a gun safely in your possession to heating your house with ammo, in which case, surely enough, accidents will happen.

What do people mean when they say that nuclear power is “safe” when compared to planes, trains and automobiles? What they mean is that the nuclear power industry has so far killed many fewer people per unit time. They have no data on how many people it will kill eventually, although by now they know that, unlike planes, trains and automobiles, which do crash and burn with some regularity, but cause limited damage, nuclear disasters do not have any definable upper bound on their destructive potential. I am pretty sure that there is enough above-ground radioactive material sitting in spent fuel pools and inside reactors to kill just about everyone. It will stay dangerous for over a million years, which is a lot longer than the expected lifetime of the nuclear power industry, or any industry, or any human civilization, or perhaps even the human race. When nuclear experts say that a nuclear reactor is safe, they can only mean that it is safe for the rest of the afternoon; beyond that they can't possibly have any actual data to support their claim. All they can do is extrapolate, given a rosy “everything will always remain under control” scenario, and that is not a valid approach. When they say that nuclear power is safe, what they are really saying is that it is safe given their perfect ability to accurately predict that the indefinite future will remain economically and socially stable, and we already know this to not be the case.

If we give up on nuclear energy, what will replace it? Nothing, probably. Let me try an example: if your lucrative murder-for-hire business suddenly runs afoul of a few silly laws (even though it has so far killed many fewer people than planes, trains or automobiles) that doesn't mean that you should keep killing people until you find another source of income. Same thing with electricity: if it turns out that the way you've been generating it happens to be criminally negligent, then you shut it all down. If you have less electricity, you will use less electricity. If this implies that economic growth is over and that all of your financial institutions are insolvent and your country bankrupt, then—I am sorry, but at this point in time that's not even newsworthy. Don't worry about that; just keep the nuclear accidents to a bare minimum, or you won't have anything else left to worry about.

That plume is at least 200 meters high and you can see large pieces (the top of the concrete containment?) separating and dropping from that height. Whatever this was on march 13, it was NOT a hydrogen explosion, like what happend in reactor 1 and reactor 4. Just compare the size of the hydrogen explosion in reactor 1 with that video of reactor 3 (you can even see the pressure wave in the video from reactor 1).

Thank you for your exquisitely timed post, kollapsnik. The news this morning (03/19/2011) is that milk and spinach have been found to have (eek!) elevated radiation. Your distinguishing the difference between radiation and radioactivity is so very important for understanding. My thoughts turn to the nastiness known as strontium-90. Elevated radiation detected in milk, I suspect, is partly from that particular nastiness. Our oh-so-helpful news from Japan is that "Eating the spinach for a year would be equivalent to 20 per cent of the radiation exposure associated with a CT scan". I would like to remind readers here that strontium-90, once eaten, does not go away. Twenty to thirty percent of it is incorporated into bones and teeth - the body confuses it for calcium - and has a half-life of 28 years. The radiation exposure to the body, due to radioactive elements now incorporated, continues and will not stop because one stopped ingesting milk or milk products. Reiterating: Measuring radiation emitted by a foodstuff is not the same as acknowledging the radioactive content.(quote from http://www.smh.com.au/world/elevated-radiation-in-milk-spinach-20110319-1c1k1.html)

I am so glad that you are back writing. There was a month long drought and was wondering if you had given up on your blog. I missed your sharp, insightful and acerbic commentary on our authorities. Keep that keyboard active, great job.Elise

Not sure how it's possible to laugh about something this serious, but I did! Repeatedly! Wonderful wit you have. I'm a pretty new reader at the Club, and I doubt I'll miss another post as long as I have an internet connection.

Thanks for addressing the widespread misunderstanding of things radioactive, which is aided and abetted by the media and the nuclear industry. The basic distinction is between the external and the internal dose. The pronouncements of no health effects are based on external doses, but the greatest hazard is from the internal dose. Comparing radiation dose from tap water, food or contaminated air to xrays, background levels and granite countertops is nonsense.

Nuclear power is the only technology that can permanently contaminate large swaths of countryside and the only one that can cause serious health effects thousands of miles away.

A more realistic (if sometimes screwball)discussion of this global catastrophe can be found at: SilentCountry.com/forum

Thanks for addressing the widespread misunderstanding of things radioactive, which is aided and abetted by the media and the nuclear industry. The basic distinction is between the external and the internal dose. The pronouncements of no health effects are based on external doses, but the greatest hazard is from the internal dose. Comparing radiation dose from tap water, food or contaminated air to xrays, background levels and granite countertops is nonsense.

Nuclear power is the only technology that can permanently contaminate large swaths of countryside and the only one that can cause serious health effects thousands of miles away.

A more realistic (if sometimes screwball)discussion of this global catastrophe can be found at: SilentCountry.com/forum

It covers completely different stuff, than you talked about, but helps people understand Sieverts and the dumb comparisons they make between being poisoned by a nuclear plant and having a chest X-ray or taking a plane ride...

I've reading these articles and am somewhat familiar with the basics of nuclear weapons / reactors. There is no way that a nuclear reactor can go critical producing a thermonuclear explosion like an A-bomb. In an A-bomb, carefully placed conventional explosives are timed to bring nuclear material together to create a nuclear explosion. This could never happen in a nuclear reactor. That said, nuclear reactors can suffer from melting where radioactive isotopes are sprayed into the air after an unforeseen accident. The ingestion of radioactive materials does have consequences beyond chest x-rays, etc., but the radiation levels beyond a few km radius outside Fukushima are not really dangerous. The dangers of the (current) situation are being overblown.

I think you are exactly correct. It was extraordinary how in the days immediately following the commencement of the nuclear crisis (and still now, though to a lesser extent) the public were reassured by numerous 'experts' that all was well. A lot of respected science blogs followed this line too - not surprising when you understand the reach of various major corporates (eg Siemens,GE et al) and their active information campaigns via seemingly impartial blogs.

For those of you that are interested, the following links have been very helpful to my understanding - possibly yours?

http://theautomaticearth.blogspot.com/2011/03/march-13-2011-how-black-is-japanese.html(and TAE's following post)http://mitnse.com/(basically factual explanations)http://techtv.mit.edu/videos/11363-mit-department-of-nuclear-science-and-engineering-briefing-on-the-japan-nuclear-crisis(curiously, one of the prof's is asked about the wisdom of using seawater to cool the rods, he said that there could be long term materials implications, degradation in terms of containment, another prof simply declined to comment - worrying I thought). I realise MIT NSE is dedicated to a nuclear future, but still interesting.and finally, a little graphic depiction of the actual fallout pattern:http://www.irsn.fr/FR/popup/Pages/irsn-meteo-france_19mars.aspx

Thanks Kathy and pandora for the linked info. It's nice to get some solid data for a change. Or so I take it to be.

A little Googling shows that Toshiba and other corporations already have on the drawing boards some untested vaporware called "nuclear batteries" or "super safe small and simple" reactors. These reputedly are to be sealed containers with but a single fuel rod each, and are to be discarded after the fuel is exhausted, much like a battery. I have an unpleasant feeling that in years to come we're likely to hear a lot of hype from nuke pushers about how safe and clean are these and similar devices. We'll be lucky if we don't end up with thousands of them rusting all over the planet a hundred years from now.

Your readers may find this page of Fukushima News and Analysis Links useful. Speaking for myself, the main thing I've learned over the last 10 days is that basically every positive, or somewhat neutral, idea I've come to hold re nuclear energy has been implanted by an ongoing Pro Nuke PR campaign that was licking its lips at the prospect of building all those new nuclear plants to 'help save us from CO2'. The other thing I learned is that we're happily burning all the coal and oil we can burn, so there is no CO2 savings in any absolute sense, just an expansion of the baseline grid loads.

Greg Reynolds: there's a lot more to making a supercritical mass than just how much of it there is. There are only a few materials that are useful for supercriticality, and natural uranium isn't one of them. The MOX reactor (that'd be the one with the uranium plutonium mix) might get closer as it has plutonium mixed with the uranium, but even then it's a long way away. The gulf between reactor grade actinides and bomb grade actinides is pretty immense.

Obviously there is enough fissile material to reach of critical mass, otherwise the reactor wouldn't work. And just as obvious, nuclear reactors are not working with natural uranium ores.

Doesn't a supercritical mass depend on the material, the shape, the density, etc. (it has been 35 years since I sat in a physics class...) ? Once molten, won't the denser materials settle to the bottom ?

How much fissile material is held in a reactor core and 50 years of spent fuel rods ? Wasn't the first atomic bomb made with something like 125 pounds of uranium ? Looking at the pictures of a reactor core, it sure looks like there is more than a 250 cubic inches of rods ( i.e. a cylinder 6inches in diameter and 2 feet long) . Granted, there is nothing to scale it by, but still...

Can you rule out the possibility of a nuclear explosion (rather than a dirty bomb type explosion)from a GE Mark 1 reactor with the spent fule stored on top of the reactor ? If so, please do so.

Nicely written piece, that hopefully will bring comprehension to a few more minds previously in denial.A couple of minor factual errors: * So far as I can tell there has been zero pumping of cooling water into the reactor pressure vessels since sometime soon after the tsunami wiped out the diesel backup generators, then the battery backup expired. The pressure vessel makeup pumps are reportedly steam-driven, but require electricity for control systems. Notice that when they finally achieved reconnection of grid power to the site on the 23rd and tried to restart the pumps, _then_ they discover the pumps are kaput. All they could do with the pressure vessels was vent them, to prevent pressure exceeding the burst limit. And this seems to still be the case. The only 'water cooling' that has been going on, is via heli-drops and fire truck spraying into the ruins, attempting to top up the spent fuel pools. Which are currently spent fuel rod adhoc furnaces - water, rubble, loose fuel pellets and remaining rod sections in the bottom, and rubble, exposed burning rods and loose pellets in the upper section. The best summary phrase: 'burnt to the lowering waterline'. Random citicalities possible in loose pellet piles in both the bottom and upper parts of the settling rubble stack. Ongoing smaller hydrogen explosions reportedly occuring in the upper section.* Theoretically, the spent fuel pools above the four Fukushima reactors do not contain ALL the rods used through the life of the reactor. The rods are supposed to only be kept in the reactor building SFP for about 18 months, while their activity drops off somewhat. Then they are put in a transport cask, and transfered to a main onsite storage pool (which is at ground level, and also suffered severe tsunami damage.) However, who knows how strictly that policy was adhered to at Fukushima Dai-ichi. Not as if TEPCO will ever release a detailed spent fuel rod location inventory.

I totally agree with your conclusion: "if it turns out that the way you've been generating [electricity] happens to be criminally negligent, then you shut it all down. ..."Here is TEPCO's criminal negligence: http://everist.org/pics/Fukushima/Fukushima_fuel_tanks.jpg Before/after washed away fuel tanks.

Two reasons why we cannot use nuclear fission power.First reason is a matter of practical energy return vs energy invested in the process. Research the term EROEI - energy return on energy invested. All studies of the EROEI of various energy sources, that take into account 'whole life cycle' cost/benefits, show some pretty shocking results. Finding out about this is what killed my optimism regarding most 'renewable' energy sources - wind, solar, wave, alcohol. But for nuclear fission, it's even worse than 'poor performance'. Turns out nuclear, when you add in the long term costs of waste materials containment, is NET ENERGY NEGATIVE. By a wide margin. For that reason alone nuclear isn't a solution.

However the *main* reason we must not use nuclear fission (of any form) is that we, as a culture, don't have an instinctive understanding of the types of major natural disasters that can and do occur on Earth with regularity. We're not conscious of them, because there haven't been any really major ones in the interval of recorded history (yet).Earthquakes and tsunamis are one thing, and bad enough as demonstrated in Japan. But the real reasons we can't use nuclear fission power stations, are: major meteorite strikes and supervolcanos. They happen, and much more often than most people realise. I collect discoveries of geological 'major strikes', and there are a lot of them. The Earth would look like the Moon (covered in craters) except they get weathered away,and eventually subducted. The point is that such events wipe out large areas, but in a 'rapidly healing' way. No long half-life isotopes.With many nuclear power stations and waste repositories present over say a quarter of the globe getting whacked by an ocean strike, not to mention failure of maintenance at all nuclear sites worldwide in the centuries subsequent to such a strike, you are talking total extinction of life on Earth for millions, possibly billions of years, due to hugely raised background radiation levels.

This is why we must not use nuclear fission power. All support for nuclear power argues in ignorance of this crucial reality.

If we can get nuclear power working in a way that doesn't involve large volumes of long-life radioactives, then fine, I'm all for it.Something like small, portable nuclear fusion with no radioactive waste products would be ideal. If only...

Millions of Japan's citizens will die prematurely because of these meltdowns. These are real 100% melt-downs ladies and gentlemen. It is too bad with all the multi-media entertainment, noone invented a morning after interactive with multiple brain stimulator attachments to simulate different levels of the nausea, depression,physical pain and weakness and the rest that come along with the trauma of being exposed to excessive radiation. Perhaps the Fukushima plant builders and authorities responsible would like to volunteer their bodies for creation of such a set of stimulation levels and data accumulation. All for science and medicine development. Withgovernment funding extracted from GE assets..

I quit building nukes in 1975 because they had no way to store or use spent fuel. They still can't as it burns through ANYTHING and must be stored in demineralized water or diluted which leads to another huge problem. Spent fuel rods all over hell and gone. Still no end in sight.

Excellent explanation for us lay readers. Nuclear diasters for dummies. I guess they didn't learn from strontium 90 fallout after above ground testing, 3 Mile island, Chernobyl, now this. Humans playing with nuclear power, like children playing with TNT. Not a good idea. Makes me believe all the more that predictions like this will come to pass alot sooner than we think, expect, or predict http://www.foxnews.com/scitech/2011/03/02/humans-verge-6th-great-mass-extinction-experts-say/

Looks like we are well under way. Toss in fossil fuel depletion, climate change, and other man made disasters and it's a fate accomplished

All that's required for criticality is enough U-235 atoms in close proximity. This has happened many times in the course of processing nuclear fuel, in numerous accidents at Russian processing plants (and sometimes at American ones.) Often it involved pouring a solution of a compound containing enriched uranium into the wrong vessel. A steam explosion could result, or sometimes just a burst of radiation. See:

The film A is for Atom gives a good political-economic history of nuclear energy. It's just amazing how immaturely the industry developed, with cost and profits trumping safety every time. For example, the GE and Westinghouse reactors were just oversized simplest reactors for submarines (see from 21:00 there) with little adaptation. In particular, containment problems under cooling failure were quickly foreseen. Advisory committee scientists had warned AEC in 1966 that new reactors near NY and Chicago should have improved dessins, and their letter should had been published by law. But the chairman Seaborg saw too much trouble for the industry, and vows to negotiate privately - but pushing for a change in the whole manufacturing system was not a feasible approach for him. The industry bluffed that they would stop selling reactors if forced to deal with containment issues seriously...